Antibodies have been conjugated to a variety of cytotoxic drugs, including small molecules that alkylate or crosslink DNA (e.g. duocarmycins and calicheamicins or pyrrolo-benzodiazepine dimers, respectively), or disrupt microtubules (e.g. maytansinoids and auri-statins) or bind DNA (e.g. anthracyclines). One such ADC comprising a humanized anti-CD33 antibody conjugated to calicheamicin—Mylotarg™ (gemtuzumab ozogamicin, Wyeth)—was approved in 2000 for acute myeloid leukaemia. In 2011, the US Food and Drug Administration (FDA) approved Adcetris™ (brentuximab vedotin, Seattle Genetics), an ADC comprising a chimeric antibody to CD30 conjugated to monomethyl auristatin E (MMAE) for treatment of Hodgkin's lymphoma and anaplastic large cell lymphoma.
Duocarmycins, first isolated from a culture broth of Streptomyces species, are members of a family of antitumor antibiotics that include duocarmycin A, duocarmycin SA, and CC-1065. These extremely potent agents allegedly derive their biological activity from an ability to sequence-selectively alkylate DNA at the N3 position of adenine in the minor groove, which initiates a cascade of events leading to tumour cell death.
WO2011/133039A discloses a series of novel analogues of the DNA-alkylating agent CC-1065 and HER2-targeting ADCs thereof. In Example 15, a number of trastuzumab-duocarmycin conjugates were tested against N87 (i.e. HER2 IHC (immunohistochemistry) 3+ gastric tumour) xenografts in nude mice. The results are shown in FIGS. 4A, 4B and 4C. After treatment with a single dose of 12 mg/kg i.v., all six ADCs reduced the tumour volume and improved survival compared to the antibody trastuzumab itself and control vehicle, without negatively affecting body weight. It was concluded that conjugates that contain a relatively short linker have a better (antitumor) efficacy than the corresponding conjugate with a relatively long linker, and that both the nature of the linker and the nature of the drug were demonstrated to have an effect on efficacy as well.
Breast cancer remains the most common malignancy among women worldwide. Breast cancer is a heterogeneous disease, which exhibits a wide range of clinical behaviours and prognoses. Breast cancer is an abnormal malignant growth of epithelial cells of the milk lobules or ducts of the mammary gland. The cancer tissue can be exclusively located on the place of origin (cancer in situ) or can have invaded through the basement membrane into the surrounding tissue (invasive cancer). Metastatic cancer occurs as soon as the cancer cells have spread by way of lymph and blood vessels to other organs. Histological differentiation and characterization of the breast cancer cells is performed with use of biomarkers.
Molecular classification of breast cancer for therapeutic decisions mainly consists of the assessment of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression status. This implies that globally three types of breast cancer can be discerned: (1) breast cancer tissue with expression of hormone receptor (ER or PR) without over-expression of HER2, (2) breast cancer tissue with over-expression of HER2, with or without expression of hormone receptor (HR), and (3) breast cancer tissue that has no therapeutically relevant hormone receptor or HER2 receptor expression, so-called triple negative breast cancer (TNBC).
Breast cancer patients with hormone receptor (HR) positive cancer tissue status (ca. 60-70% of all breast cancer patients) have a better prognosis than those without or with minimal hormone receptor status. On the contrary, patients whose tumour has an IHC 3+ or IHC 2+/FISH (fluorescence in situ hybridization) positive status (occurring in about 20% of all breast cancer cases) have a worse prognosis in comparison with breast cancer patients whose tumour has a lower grade of HER2 membrane expression or a FISH negative amplification rate. Now that patients with hormone receptor positive and HER2 over-expressing breast cancer tissue have the option of targeting therapy, triple negative breast cancer implies the worst prognosis, as only chemotherapy with limited efficacy is available for these patients whose tumour is ER, PR and HER2 negative.
Herceptin™ (trastuzumab), a recombinant humanized IgG1 monoclonal antibody against HER2, was approved in the US by the FDA in 1998 for adjuvant treatment of HER2 over-expressing breast cancer and for the treatment of metastatic HER2 over-expressing breast cancer and gastric cancer, i.e. HER2 IHC 3+ or HER2 IHC 2+/FISH positive. The drug was approved in Europe by the EMA in 2000.
Clinical studies with patients who have metastatic breast cancer disease have demonstrated, that there is only clinical relevant efficacy of trastuzumab treatment if the patient has a tumour with HER2 IHC over-expression or FISH positive gene amplification. For this reason, current HER2 testing algorithms are aimed at identifying those patients most likely to achieve a significant benefit from HER2 targeting. Whereas HER2 membrane expression is biologically a continuum from low to high over-expression, approved IHC tests, like the HercepTest™ (Dako, Glostrup, Denmark), categorize HER2 status on a semi-quantitative scale ranging from 0 to 3+. An IHC score of 3+ is assigned if there is a strong circumferential membrane staining in >10% of the cancer cells. FISH positive gene amplification is assigned if the amplification rate relative to the centromere is ≧2.0. It identifies patients who might have a benefit of treatment with trastuzumab or other HER2 targeting agents. A review of 6,556 breast cancers revealed that about 92% of tumours with a HER2 score of 3+ had FISH positive gene amplification. Conversely, HER2 amplification was observed at lower rates in tumours with scores of 2+(23.3%), 1+(7.4%), and 0 (4.1%). With HER2 amplification as an established predictor of response to HER2 targeting agents, the current algorithm calls for FISH testing of tumours with a HER2 IHC score of 2+.
Ado-trastuzumab emtansine or trastuzumab emtansine (Kadcyla™, T-DM1) is an ADC in which trastuzumab is conjugated to the cytotoxic maytansine anti-tubulin agent DM1. T-DM1 has antitumor activity in tumour xenograft models that are not responding to therapy with trastuzumab as single agent. In the Phase 3 EMILIA trial, patients with HER2 positive advanced breast cancer, previously treated with trastuzumab and a taxane, were randomly assigned to receive T-DM1 or lapatinib plus capecitabine. T-DM1 treatment effectuated significantly longer progression-free and overall survival time in comparison to the treatment of the control group.
Kadcyla™ (T-DM1) was approved in the US by the FDA in February 2013 for the treatment of patients with HER2-positive metastatic breast cancer who received prior treatment with trastuzumab and a taxane. The drug was approved in Japan by the MHLW (Ministry of Health, Labour and Welfare) in September 2013 and in Europe by the EMA in November 2013. The currently approved regimen comprises a dosage of 3.6 mg/kg body weight i.v. every three weeks. A dosage of 2.4 mg/kg body weight i.v. weekly is investigated in an ongoing Phase II study with a combination of T-DM1 and capecitabine for the 2nd line treatment of patients with breast cancer or gastric cancer and in an ongoing Phase III study to investigate T-DM1 against a taxane as 2nd line treatment of patients with gastric cancer. A Phase ITT study is also ongoing for the combination of T-DM1 with pertuzumab for the treatment of patients with HER2 positive, locally advanced, or metastatic breast cancer.
Despite the improvement that the introduction of T-DM1 in clinical practice brought over trastuzumab for the treatment of HER2-positive metastatic breast cancer, the use of T-DM1 is associated with a number of serious side-effects, most importantly thrombocytopenia, hepatotoxicity, and neuropathy (irreversible axonal degeneration). Furthermore, neither trastuzumab nor T-DM1 are authorized for the treatment of human solid tumours and haematological malignancies with moderate or low HER2 expression, i.e. IHC 2+ or 1+ and/or FISH negative HER2 amplification status of the cancer tissue.
In analogy to breast cancer, HER2 expression indicates a poor prognosis for patients with ovarian cancer (A. Berchuck et al., 1990, Cancer Res., 50, 4087-4091; H. Meden and W. Kuhn, 1997, Eur, J. Obstet. & Gynecol. Reprod. Biol., 71, 173-179). SKOV3 cells are derived from the ascites fluid of a patient with ovarian adenocarcinoma. This cell line is over-expressing HER2 and is frequently used for in vitro and in vivo explorative investigation of HER2 targeting agents. Trastuzumab and pertuzumab have several anti-cancer effects in this cell line (N. Gaborit et al., 2011, J. Biol. Chem., 286, 13, 11337-11345). Monotherapy with the anti-HER2 antibodies trastuzumab and pertuzumab thus far had modest efficacy (G. M. Mantia-Smaldone et al., 2011, Cancer Management Res. 3, 25-38; S. P. Langdon et al., 2010, Expert Opin. Biol. Ther. 10:7, 1113-1120). The antitumor effect is markedly increased if a HER2 targeting antibody is combined with chemotherapy (S. Makhija et al., 2010, J. Clin. Oncol., 28:7, 1215-1223; I. Ray-Coquard et al., 2008, Clin. Ovarian Cancer, 1:1, 54-59).
Further, a high medical need exists for the treatment of late stage bladder cancer disease. Chemotherapy, e.g. the combination of cisplatin and gemcitabine for advanced or metastatic bladder cancer, has limited efficacy as it effectuates in the mean a response rate under 50%, whereas patients have an overall survival time of 6 to 12 months. In case of resistance to chemotherapy there is no standard therapy option at all. HER2 positivity was significantly associated with reduced complete response rates (50% versus 81%, p=0.026) after chemo-radiation (A. Chakravarti et al., 2005, Mt. J. Radiation Oncology Biol. Phys., 62:2, 309-317). Addition of trastuzumab to a regimen of paclitaxel and carboplatin as first line therapy of HER2 positive advanced bladder cancer showed an overall response rate of 70% and an overall survival time of 14.1 months in a Phase II study (M. H. A. Hussain et al., 2007, J. Clin. Oncol., 25:16, 2218-24). In a casuistic application, a patient with a tumor relapse after standard chemotherapy responded to the combination of trastuzumab, paclitaxel and carboplatin (D. Arnsellem-Ouazana et al., 2004, Ann. Oncol., 15, 3, 538).
In case of invasive non-small-cell lung cancer adenocarcinoma, HER2 mutation and amplification are related with unfavorable outcome (M. Suzuki et al., 2014, Lung Cancer, http://dx.doi.org/10.1016/j.lungca.2014.10.014). In lung cancer patients with HER2 mutation, a disease control rate of 93% could be effectuated with trastuzumab-based therapies (J. Mazieres et al., 2013, J. Clin. Oncol., 31:16, 1997-2004). Chemo-resistance of lung cancer often is associated with enhanced HER2 expression (C.-M. Tsai et al., 1993, J. Natl. Cancer Inst., 85:11, 897-901; Z. Calikusu et al., 2009, J. Exp. Clin. Cancer Res., 28:97) and resistance to tyrosine kinase inhibitors is correlated with enhanced HER2 amplification (K. Takezawa et al., 2012, Cancer Discov. 2(10), 922-33).
Patients with early or advanced prostate cancer mostly receive an androgen receptor targeting therapy. There is a cross-talk in the signaling functions of the androgen receptor and HER2 (F.-N. Hsu et al., 2011, Am. J. Physiol. Endocrinol. Metab., 300:E902-E908; L. Chen et al., 2011, Clin. Cancer Res., 17(19), 6218-28). HER2 activation suppresses the expression of the androgen receptor (C. Cai et al., 2009, Cancer Res., 69(12), 5202-5209), increased HER2 expression is associated with PSA progression, rapid proliferation and poor prognosis (S. Minner et al., 2010, Clin. Cancer Res., 16(5), 1553-60; S. F. Shariat et al., 2007, Clin. Cancer Res., 13(18), 5377-84). Increased expression of HER2 seems to be involved in progression to androgen independence in about a quarter of prostate cancer cases (J. M. S. Bartlett et al., 2005, J. Pathol., 205, 522-529).
Pancreatic cancer is among the most lethal human solid tumors due to its insidious onset and resistance to therapy. Gemcitabine or the combination of 5-FU, leucovorin, irinotecan, and oxaliplatin can help prolong life in patients with advanced disease (H. Burris and A. M. Storniolo, 1997, Eur. J. Cancer 33(1):S18-S22; T. Conroy et al., 2011, N. Engl. J. Med. 364(19):1817-25). More recently, it was reported that HER2 expression is also prevalent in pancreatic cancer with an equal proportion of 10% designated as HER2 2+ and 3+. Based on this fact, HER2-targeted treatment comprising trastuzumab is considered as a viable option in this patient population based on effects observed in pre-clinical models [C. Larbouret et al., 2012, Neoplasia 14(2), 121-130).
Using accepted staining and scoring methods, over-expression of HER2 was observed in approximately 6% of colorectal cancer (CRC) patients (A. N. Seo et al., 2014, PLoS ONE, 9(5): e98528). Based on this, HER2-targeting treatment may be effective in this subset of CRC patients. Two clinical trials have investigated the benefit of trastuzumab-containing combination therapy in advanced or metastatic CRC and clinical responses were observed in these trials providing evidence of treatment efficacy (R. K. Ramanathan et al., 2004, Cancer Invest. 22(6): 858-865; J. Clark et al., 2003, Proc. Am. Soc. Clin. Oncol. 22: abstr 3584). Moreover, one study suggested the inclusion of trastuzumab therapy as part of treatment regimens for (anti-EGFR monoclonal antibody) cetuximab-resistant CRC patients (A. Bertotti et al., 2011, Cancer Discov. 1(6): 508-523).
The management of advanced head and neck squamous cell cancer or carcinoma (HNSCC) consists of multiple-modality therapy with surgery, radiation, and chemotherapy. Beckhardt et al. reported high HER2 over-expression in 16% of cell line samples, and moderate and low HER2 expression in 31% and 35% of samples, respectively (R. N. Beckhardt et al., 1995, Arch. Otolaryngol. Head Neck Surg. 121:1265-1270). This illustrates the potential therapeutic potential of trastuzumab treatment in HNSCC.
In 1999, Gorlick et al. reported over-expression of HER2 in 20 of 47 osteosarcoma samples, and showed that these patients had a poor response to therapy and a decreased rate of survival compared with patients whose tumors did not over-express this antigen (R. Gorlick et al., 1999, J. Clin. Oncol. 17:2781-8). Hence, HER2 emerged as a promising candidate for targeted biologic therapy in this indication. Recent findings from clinical investigation using trastuzumab indicate that anti-HER2 treatment can be safely delivered in combination with anthracycline-based chemotherapy and dexrazoxane (D. Ebb et al., 2012, J. Clin. Oncol. 30(20), 2545-2551).
Further, HER2 over-expression is seen in approximately one-third of acute lymphoblastic leukaemia (ALL) patients, even more frequent in the presence of the Philadelphia translocation. Inhibition of HER2 induces apoptosis of the leukemia cells in vitro (M. E. Irwin et al., 2013, PLoS ONE, 8:8, e70608). In a Phase II study, it was demonstrated that trastuzumab treatment of refractory or relapsing adult B-ALL patients with HER2 over-expression in malignant B-cells resulted in an overall response rate of 13%, which shows the response of this disease to a HER2 targeting agent (P. Chevalier et al, Blood, 2012, DOI 10.1182/blood-2011-11-390781).
Hence, there is a need for new HER2-targeted therapies, notably for treating patients with tumours and malignancies that have (i) a moderate or low IHC status, and/or (ii) a negative FISH status, and/or (iii) a hormone receptor (HR) negative status of the cancer tissue. Particularly, new regulatory approved therapies are needed for the targeted treatment of triple negative breast cancer (TNBC).